Vanilla extracts comprising vanillin and other vanilla flavor compounds are produced by subjecting ripe green vanilla beans to a curing and extraction process. The curing process releases vanillin from glucovanillin and forms the brown-black whole vanilla beans commercially available. The cured beans can then be extracted to form a liquid vanilla extract.
The curing period usually lasts many weeks or months, involves repeated quality controls and depends on the environmental conditions. While the sensory profile/flavor of the resulting extracts can be excellent, even under optimal conditions the vanillin yield is very low and usually up to about 2.2% per dry weight of vanilla beans. Shorter curing and extraction processes known in the art either result in a similarly low average vanillin yield, and/or the sensory profile is not fully developed/less complex with an unbalanced flavor profile, and/or contains off-notes. One example of such a process is in U.S. Pat. No. 3,663,238, which describes a curing/drying process for green vanilla beans in a sweating tank that involves cutting green beans and incubating them at 140° F. (60° C.) for 70-78 hours and drying them with forced air at the same temperature to a moisture content of 35-40%, and at room temperature to a final moisture content of 20-25%.
The long curing period of traditional processes employs naturally occurring enzymatic reactions. The enzymatic reactions in the vanilla beans from its precursor glucovanillin to vanillin are believed to be mainly caused by residual plant enzymes, in particular glucosidase enzymes.
Notably, B. subtilis was not previously known to be involved in or useful for the production of vanilla flavour compounds in vanilla beans. The bacterium was known merely for being capable of expressing various enzymes, including, among many others, the b-glucosidase enzyme.